Suggestion: find a Hertz receipt for a domestic rental where you used your corp CDP code and you entered your FF# for a domestic airline. If you find no line item on the final receipt charging you for FF miles then I can say confidently that the corp code does not allow for FF miles accrual.

If you can't find an old receipt then you could call Hertz and ask about the rules for that corp CDP.

I find it very frustrating with most rental companies that one is not alerted to rules like this when booking on line. With the biggies if I enter in a coupon code that requires x-number of days of rental to qualify the web site (most of the time) will alert me to this. The same could be said for requirements of the code for a particular car class and when the dates of the rental are outside the expiration date for the coupon. But when it comes to whether the discount code (as opposed to coupon code) will allow for miles accrual I don't recall ever being notified of this EVEN if I put my FF# in the reservation. Kinda crappy IT if you ask me.

Here is another suggestion: many agencies (not sure about Hertz) will allow for the accrual of miles on foreign carriers WITHOUT a FF miles surcharge. So you might still be able to earn miles using your corp CDP if the miles go into a FF program outside the U.S.

There is more here on FF miles surcharges: The car rental FF miles surcharge thread.

There is a great tip about omitting your domestic FF# until the rental is complete (and receipt is closed) and then LATER requesting the miles.... and Hertz is specifically mentioned!!! You can avoid the FF surcharge. Not sure if this would work if your corp CDP disallows FF miles entirely. See post #6 of that thread.

You can also find info about the foreign carrier exception at mile marker #16 of that thread. Again, not sure if your corp CDP will allow for earning miles even if those miles are free.

One final suggestion: check out my collection of current promos at the thread Q3 2010 Car Rental Bonus Promos!